THE GLASS HOUSE The Eden Project endeavours to both recognise our countrys great past heritage of plant exploration and at the same time look to the future. Helping to define, through research, a world where mankind can live and develop within sustainable parameters. To design the built form of a glasshouse, and to represent these ideals, requires both an understanding of the architectural heritage that made our past botanical achievements possible, and ideas for a more sustainable future.
Trang 1THE EDEN PROJECT GLASS HOUSES WORLD
ENVIRONMENTS
Andrew Whalley B.Arch AA Dipl AIA RIBA
Director Nicholas Grimshaw & Partners
T H E G E N E S I S O F E D E N
Without plants there would be no life on earth
Plants are unique in their ability to convert the energy
of the sun through photosynthesis and supply us with our
lifeline support systems
Oxygen - food - fuel - medicines - clothes
Even our use of fossil fuels coal gas and oil are
exploiting the results of photosynthesis from millions of
years ago
Our increasing understanding of horticultural sciences,
exploration of the world and exploitation of plants is
inexorably entwined with the development of our
civilisation and the potential of mankind
The Earth Intensive farming Sunflowers
T H E G L A S S H O U S E
The Eden Project endeavours to both recognise our
country's great past heritage of plant exploration and at
the same time look to the future Helping to define,
through research, a world where mankind can live and
develop within sustainable parameters To design the built
form of a glasshouse, and to represent these ideals,
requires both an understanding of the architectural
heritage that made our past botanical achievements
possible, and ideas for a more sustainable future
As a nation of adventurers we have developed
navigational and seafaring skills that have allowed us to
explore the globe The ports of Cornwall were the first
landfalls encountered by many returning eighteenth and
nineteenth century sea captains, many of whom collected
plant specimens on their travels Captain Cook was well
known for his scientific interests and most ships'doctors
in particular had great scientific interest in what they saw and collected on their travels In parallel with the work of such famous botanists as Sir Joseph Banks was the emergence of a new architectural form to house and protect these new and delicate specimens, a built form that could transform the temperate climate of the British Isles into the humid tropics -the Glass House
The first half of the nineteenth century is the period of rapid change during which the demand for more exotic specimens in turn demanded much higher levels of natural light than was provided by masonry buildings with large windows
In 1811 Thomas Knight, head of the Royal Horticultural Society, set out a challenge:
" not a single building of this kind has yet been erected
in which the greatest possible quantity of space has been obtained and of light and heat admitted - proportionate
to the capital expended."
Interestingly this statement was almost repeated verbatim
by Peter Thoday at our first briefing session on the Eden project
Sir Joseph Paxton is synonymous with the emergence of this new design approach He introduced industrialised and prefabricated techniques that produced great economies and speed of construction However it is interesting to note that all of his work including the Great Stove at Chats worth (1841) and indeed the Great Exhibition of 1852 kept to the relatively safe and known technologies of timber construction A bigger influence
on the new architectural form was through the exploitation of new technology
The Great Stove, Timber glazing systems,
Trang 2In 1816 John Claudius Loudon patented a technique that
exploited the malleable qualities of wrought iron,
drawing and curving it into a structural glazing sash bar
Immediately he saw that this technology offered
possibilities for a new type of Architecture In his own
words:
" it may be beautiful without exhibiting any of the orders
of Grecian or of Gothic may not therefore glass roofs
be rendered expressive of ideas of a higher and more
appropriate kind, than those which are suggested by mere
sheds or a glazed arcade."
Glass during this period was still taxed, and this was
applied relative to the size of the panes Glass was also
still an expensive luxury material produced by spinning
plates or cutting it out of cylinders Consequently it was
highly desirable to construct these new plant houses with
their huge expanses of glass using many small sheets
rather than large sheets
Traditional timber glazing bars with small sheets of glass
were relatively inefficient in comparison to the slender
wrought iron glazing bar; this produced the optimum
transparent skin Loudon developed his system with the
contractor W and D Bailey using the glass as part of the
structural system This gave rise to completely new
expressions of architectural form Many of these glass
houses were lost during the early part of the twentieth
century Fortunately one example remains to this day at
Bicton in Devon Its very light filigree structure is
reminiscent of the delicate structure of a leaf
6 Bicton Gardens, Devon, J C Loudon
Conservatory, Liechtenstein Leaf structure
Castle
The Palm House at Kew, built in 1848, uses the same
technology and is far better known It, also, demonstrates
the value of collaboration, this time between the architect
Decimus Burton with the intuitive engineering expertise
of Richard Turner They both answer the challenge from
Thomas Knight by harnessing the best of the current technological understanding and generating new architectural solutions that were truly great expressions of the era
Palm House, Kew Palm House Kew Kibble Palace, Glasgow
It is interesting to contrast this to the temperate house designed by Burton ten years later, without the ingenuity
of Turner, where a pre ordained architectural form takes over
The development of this very organic exploration of design solutions probably culminates in the soft rolling forms of Kibble Palace, originally constructed in 1865 and later dismantled, shipped and reassembled in Glasgow's botanical gardens Certainly this building was enormously influential on myself during my time studying at the Mackintosh School of Architecture, and was a very strong influence as we explored solutions for the Eden Project
Paxton's ridge and furrow glazing at Chatsworth with its east west orientation minimised the loss of sunlight due to the reflective nature of glass At the same time he had developed new mechanised prefabrication techniques that delivered an improvement in construction times and
Paddington Station, 1 K Brunei 1854
Trang 3construction efficiencies The influence of the Great
Exhibition (1852) on I K Brunei's Paddington Station
(1854) is well-documented; both were built by Fox
Henderson Undoubtedly the techniques that had been
developed for the glass house were transferred and
developed for the demands of the latter nineteenth
century: the large Railway sheds
This sequential influence took root in our own work when
we came to design Waterloo International Terminal
There had in fact been little in the way of ail way
architecture since the nineteenth century in the UK The
terminal would symbolise not only a new renaissance of
high speed rail travel but also a new permanent
connection and gateway to mainland Europe The roof,
although only 10% of the overall building budget, was to
be the signature and emblem of this new service
International Terminal, Waterloo Station, 1992
The technical challenge was to design a roof structure and
envelope that could deal with the twisting and diminishing
geometry of the track alignment For speed and economy
the glazing had to use standard rectilinear sheets of glass In
collaboration with the engineer Anthony Hunt Associates
we developed the steel and glass roof that took on the
sinuous shape of the tracks below
This is in fact where the line of thought turns full circle Glass Houses to Railway Halls and back to Glass Houses It was because of our work at Waterloo that the team were asked to prepare proposals for the Eden Project Eden
International Terminal, Waterloo at night
E D E N
Our brief was to create a showcase for global biodiversity and human dependence on plants The structures were to be large enough to allow the exhibition and study of a range of plants on a hitherto unachievable scale Within the first phase two climate capsules were to be recreated from different world environments (biomes)
The humid tropics (rain forest) and the warm temperate (Mediterranean) biomes were to be constructed as enclosures; a third zone, the temperate, was to be in a sheltered external area
It was the team's goal from the outset that the project should both entertain and educate at the same time The creation of natural habitat zones that have the height and volume to allow plants to grow in a natural way, to their full mature height, has seldom been done; we believed it required fresh thinking
With the humid tropics this required an enclosure that would allow trees to mature and form a canopy at forty metres in height, setting a clear span building height of fifty metres
Botanical science has developed from the nineteenth century encyclopaedic cataloguing of specimens Now, in the twenty first century, science is exploring our understanding of biodiversity and the importance of genetic grouping and ecosystems Our goal was to develop an architectural response that was informed by these new demands in the same way that our predecessors had, almost two hundred years ago
Finding the right site for this new botanical garden was critical The original sites that were considered were the clay workings at Roche The 'Clay Alps' were mountainous heaps of clay and spoil; apart from the difficult ground conditions they were also highly exposed
The final chosen site was an old clay pit that was coming to the end of its useful life This hollow in the ground provided the inspiration for our design solutions
Trang 4The Bodelva china clay pit, St Austell, Cornwall
T O P O G R A P H Y A N D F O R M
Our starting point was to use the contours of the clay pit
as an integral part of the architecture, using the quarry
wall as one side of each biome This had the advantage
of creating great spatial drama and a terraced profile as
staging for the planting , thus creating drama from day
one, even when many of the plants would be relatively
immature
A three dimensional model was created on the computer
to explore the potential sites for the biomes This was
assessed by looking at both the topography and potential
solar orientation Sun path analyses were used to find the
optimum location for each biome
Early concept of 'arch' scheme Early concept sketches
Ground model of existing site topography
The inevitable protracted funding process gave us time to thoroughly evaluate our proposals There were the logistical problems of transporting large steel trusses in Cornwall The quarry was also changing shape as the last
of the clay was extracted, effectively meaning that our ground terrain was constantly changing as we tried to complete our proposals
N A T U R E A N D E F F I C I E N C Y
There are many influences during any design process During the development of Eden we often referred to the Science Fiction film from the early seventies entitled 'Silent Running' This centres around a series of very light weight biomes replicating the earth's principal climate zones, all floating in outer space The concept of these biomes helped to encourage us in our conviction to explore new and innovative technical solutions for the structure and envelope At this time we were appraising light weight foil as an alternative to glass and we wanted
a solution that would capitalise on the properties of this ultra light weight material, in a similar way as Louden's wrought iron system did for glass
Our first proposals built upon our work at Waterloo with
a series of diminishing primary steel trusses connected to
each other with a secondary system, supporting a ridge
and furrow glazing system that would have been familiar
to Paxton However at this stage we had established the
idea of a free form in plan and section that hugged the
contours of the pit
" % r f i * > i r r
-Image from the film 'Silent Running'
Trang 53 K ^ ^ M ^ t ^ S
Responsive structural system, Andrew Whalley & Chris McCarthy
On a previous project I examined, with the engineer Chris
McCarthy, a responsive structural system that could adapt
to changing loading conditions Forces could effectively
be moved around the system in the way a body does with
bones, muscles and tendons This skeleton carried an ultra
light weight skin formed from a series of pneumatic
pillows using layers of transparent foil and spluttered
metal coated foil Again loads could be responded to by
varying the pillow's air pressure, resulting in an
extremely light weight dynamic enclosure Ideas that start
as theoretical exercises can help develop and inform later
projects
Nature has many lessons to teach both architect and
engineer; most obviously nature is based on the minimum
use of energy and the careful use of resources i.e.,
efficiency in metabolism What often appears to be
fragile is actually robust as it has an ability to adapt
Radiolaria Honeycomb
Microscopic photograph of a fly's eye
An excellent example of these efficiencies can be found
when examining the one-celled creatures Radiolaria As
they grow through centrifugal force the silica that they are
formed from takes the geometric form of the minimum
length hexagonal pattern In just the same way bees build
honey combs because they are 'busy bees', trying to achieve the maximum with the minimum effort Nature seems to continually form hexagonal structures as the most efficient way of absorbing stress
T H E E D E N S P H E R E
We resolved our concerns by finding a simple and direct solution to the geometry David Kirkland redefined the generation of the biome forms as a series of interconnecting spheres We took this computer model and intersected it with the terrain model of the clay pit, which in turn defined the final form of each biome This allowed us to develop a proposal that was independent of the exact quarry profile It also allowed us to define the surfaces as geodesic shells, that could get the most out of the long span ultra light weight nature of foil pillows
Connecting spheres Sketch of siting Spheres & structure
As with the Radiolaria the geodesic shell is formed from hexagons to minimise on tube length to surface area The size of the hexagonal grid is a proportion of the diameter
of the sphere, with the largest dome being subdivided into pillows with a diameter of approximately eleven metres
s
^^mESv' • ft" ' -*WW
• 0 * 0 , » « • • ; ^MWW\
Computer-generated image of the first 'geodesic' scheme
H O W T O B U I L D A S P H E R E ?
Everybody is familiar with the problem of representing the surface of a sphere on a two dimensional plane An orange skin can not be rolled out flat on a table, and the attempt to represent the surface of the earth on a sheet of paper leads to great distortions as far as the size of the land mass is concerned However the surface of a sphere can be subdivided into planar triangle-based surfaces similar to a football The earliest example for the realization of a geodesic sphere is Walter Bauersfelds Zeiss Planetarium in Jena, Germany from 1926
Trang 6Later, Richard Buckminster Fuller carried out substantial
research into geodesic spheres and their underlying
geometry The problem has always remained the same
How can the surface of a sphere be subdivided into a
number of building elements that:
• can be easily constructed with available
construction methods
• are ideally selfsimilar in order to reduce the
number of different components
• preserve the structural integrity of the overall
structure
T H E G E O M E T R Y O F T H E
I C O S A H E D R O N A P P L I E D AT E D E N
Like earlier predecessors our geodesic domes are based on
the geometry of the icosahedron, an element with 12
corners and 20 surfaces Circles drawn through two
adjacent comers of the icosahedron result in 'Great Circles',
because all corners of the icosahedron are positioned on the
surface of a sphere These Great Circles intersect in such a
way that 5 warped triangular and selfsimilar surfaces are
generated around each comer of the icosahedron Because
each comer of the icosahedron is surrounded by 5 triangular
zones the element directly on the comer is a pentagon The
subdivision of the sphere's surface into triangular zones
with equal side lengths is the key to finding a construction
method that applies selfsimilar sticks and varying nodes to
form the structural 'net'
The triangular base zones described above can be further
subdivided into triangular elements at a selected frequency
The body formed with planar triangles approaches the
spherical shape more and more the smaller the subdividing
triangular elements At Eden we have omitted triangles in
such a way that the zones between the pentagons are filled
with hexagons very similar to the surface of a football
Unfortunately these hexagons are not planar in a geodesic
sphere based on an icosahedron This was obviously a
problem keeping in mind that the hexagons are the basis of
our cladding panels Developing our ideas futher with
Mero GmbH a solution arose This was to apply a recently
developed theory by the Russian scientist Pavlov who
managed to work out a geodesic sphere with hexagons that
are planar and the geometry still based on the icosahedron
T H E H E X T R I H E X G R I D
The resulting net of hexagons alone could have formed
the envelope for the Eden biomes However the stick
diameters for the individual elements would have been
around 500mm It was felt that by introducing a second,
inner layer, of structure the member sizes could be
reduced substantially leading to a far more economic
structure with a more light weight appearance The inner
layer consists of triangles below the node points of the outer layer which circumscribe hexagons themselves The connection between the two layers is established with diagonals which connect the node points of both layers
We call the resulting geometry a 'hex-tri-hex' grid
Although on first appearances this is a very ordered geometric solution there is a complication in resolving the interconnection of the spheres as each has a different diameter and sub divisional grid Again a solution can be found in nature A dragonfly's wing is constructed from
a series of very light weight skins with a hexagonal cell structures These are connected to the body by a series of primary sub dividing elements When the cell system meets the primary system it simply connects in a perpendicular relationship Exactly the same can be seen with soap bubbles If they are approximately the same size they take on a hexagonal geometry If you sub divide them then again they join the subdivision at right angles Nature does not have formalist architectural hang ups!
Dragonfly wings Soap bubbles
As we developed the geometry the computer was invaluable not just as a number cruncher but as a way of exploring the spatial forms that the combination of differing diameter interconnecting spheres and the pit topography created We undertook a series of computer studies that culminated with a series of 'fly through' animations
Still from 'fly-through' animation in the Humid Tropics Biome
Trang 7E N V E L O P E
The skin of the biomes utilises Ethyltetraflouroethylene
foil, ETFE It was selected as its performance was far
better than glass in both horticultural and energy terms It
allows a far greater range of daylight to pass through in
particular the Ultra Violet part of the light spectrum Its
light transmittance quality is further enhanced by its long
span characteristics: the largest pillows at Eden span
eleven metres without any secondary structural system
Consequently there are very few light-blocking structural
members
Efficacy Transmission
(relatival
L ultraviolet tuv> -L visible light (VIS)
0.00001 + ^ — • — , , i ~ ! 1—i 1—• i i — — i — i — i — 1—i 1 r—i—i —"-^H O
250 300 3B0400 500 600 TOO nm 780
Wavelength
= • i»
Light transmission of ETFE/glass compared (information
from Dyneon GmbH)
The pillows are up to two metres deep and are formed
from three layers of ETFE foil The two air cavities are
pressure equalised by means of a small connecting
aperture but in terms of thermal transmittance they are
effectively separate The complex geometry of the
pillows - hexagonal on plan and double-segment-shaped
in section - makes U-value calculation by conventional
methods impossible Much of the cavity space is large
enough for significant convection currents to be set up A
combination of theoretical analysis (computational fluid
dynamics / finite element analysis) and empirical testing
(by means of hot-box experiment) determined that the
U-value was approximately 2.7W/m2K Therefore, in spite
of the material being 200 microns thick or less for each
layer, it performs better thermally than double glazing
As with glass it would be possible to apply low emissivity
coatings to one or more of the ETFE layers to achieve
even better performance
Our goal was also to create a solution that embodied
Eden's environmental ethos The embodied energy is
substantially better than a glass solution In material
terms it uses less than 1 % of the volume of material that
would have been used in a double glazed solution This,
coupled with a proportionate reduction in supporting
framework, again substantially reduces transportation
impact and costs The material is very light to erect so
again there is a reduction of site equipment Most
importantly it can be recycled
This desire to optimise on the properties of foil, i.e large
span pillows, has meant a great deal of research and
testing
Single-chord & bowstring Hexagon with ETFE cladding geodesic
Our original design was for a single chord hexagonal grid geodesic form with a secondary bow string cable stay support The geometry and pillow sizes were informed through discussions with the two principal foil supplying companies A whole series of solutions were then developed and considered including timber/ glue-lam and aluminium for the geodesic structure
The eventual winning contractor was Mero GmbH who offered a combined structure and envelope package As the two are intrinsically linked this was a significant advantage Their experience with this type of structure brought considerable benefits to production and assembly Their preferred material was steel and by adopting a double chord system the tubes could be kept below 200mm despite the fact that the span was 100 metres Mero's sub contractor for the envelope was another German company, Foiltec GmbH, and over a period of nine months we have developed and tested the pillow solutions
Initially the size for the biggest pillow was based on intuition - a feeling for what the largest achievable span was likely to be There were incentives on all sides to design as large a hexagon as possible:
• the larger the hexagons were, the lighter the steel would be and thus the cheaper the overall building
• bigger hexagons also meant more light and, because the frames are relatively less insulative than the pillows, better thermal performance
A hexagon side length of 5.5m, equating to a diameter of
11 m, was set as the target This resulted in pillow sizes of over 75 square metres The first stage was to establish the wind loads that needed to be accommodated A scale model of the biomes and a few square kilometres of the surrounding terrain were built and tested in a wind tunnel This was followed by full-scale tests to establish the behaviour of the ETFE under dynamic biaxial loading at varying temperatures, the strength of the welds (ETFE is manufactured in 1200mm wide strips) and the strength of the connection to the extruded aluminium frames Parallel to the empirical testing, computational non-linear analysis was carried out based on the material's physical characteristics (established by Instrom testing) By comparing the results of the empirical and theoretical analysis a clear picture was built up of how the overall system behaved under the design loads
Trang 8Testing an ETFE foil pillow in Bremen, Germany
It emerged that the 3-layer cushions were not robust
enough to construct hexagons with a 5.5m edge length!
The first solution that was attempted was to install
reinforcing cables over the pillow to reduce the effective
span of the ETFE While this was workable in principle
there were a number of disadvantages: it was a relatively
expensive solution, and was likely to cause chafing
between the steel cables and the ETFE Significantly
increasing the thickness of any individual layer was not
feasible because it resulted in embrittlement: to work
effectively the ETFE needs to maintain elasticity
In one of many round-table discussions a solution
emerged to use a double layer of foil for the
externalsurface (the part subjected to the most onerous
suction loads) The two layers would work together to
share the load A second series of tests was then carried
out which established that the proposal would work with
a margin of comfort
Test pillow in Bremen, Germany
E N V I R O N M E N T A L S Y S T E M S
Greenhouse design has frequently suffered from the
environmental control systems, both from a successful
operational aspect and from the visual impact of the
system itself Very early on, with Peter Thoday, the
horticultural consultant for Eden, we established the
plants' environmental requirements for each biome Within this context we defined the design parameters with Ove Arup
We did not want to have any sun-shading devices on the envelope and we aimed for the minimum of any mechanical devices or plant within the biomes
In principle this was achieved by using the form of the biomes for warm air reservoirs; the curved biome form would assist the natural convection currents created with air jets
'Traditional' calculation methods were used early in the design process to establish the number of air-handling units needed to supply the large volumes of heated air required Similarly the strategy for ventilating the Biome enclosures was established, involving a combination of opening glass louvres at low level, with hinged panels at the top of each dome to exhaust hot air
As the design progressed, Ove Arup & Partners undertook a number of more detailed studies to refine the environmental systems In particular a Dynamic Thermal Model was used to calculate the thermal conditions within the Biomes for typical days in selected months This study then provided the data
to allow a detailed study of air movement within the Biomes using Computational Fluid Dynamics (CFD)
CFD analysis was carried out for the Humid Tropics and Warm Temperate Biomes during Winter and Summer conditions These studies produced predictions of environmental conditions in terms of air temperatures and velocities; the results broadly followed the conclusions of the initial calculations Critically, however, the CFD model allowed us to assess the effects of removing, or relocating, some of the air-handling units This proved important as the terrain around the Biomes makes access to some areas difficult both for initial installation and subsequent maintenance of the mechanical plant Consequently we were able to fine-tune the mechanical systems, omitting a number
of air-handling units and relocating others to areas of easier terrain, whilst maintaining the required environmental conditions within the Biomes
One interesting result of the CFD study relates to the effect of air movement on the plants within the Biomes In normal greenhouse conditions plants tend to grow with relatively weak stems due to the lack of wind We have discovered that air speeds within the Eden Biomes will tend to strengthen the plants; ripples of air movement recreating natural conditions
to produce specimens as close as possible to their counterparts in nature
T H E G A R D E N
Throughout the project we have continued the same philosophy towards sustainability, challenging the way
we have previously considered designing buildings The visitor centre is a prime example Again it is built into the topography of the pit with part of the building sunk into the terrain with a grass roof To keep the embodied
Trang 9energy of the building to a minimum we have used
materials from the site in the form of gabion walls using
site rocks Soil from the pit has been used to construct
rammed earth walls and much of the cladding utilises
light and economic cedar wood shingles
The Visitor Centre
A very similar approach can be found in the "Biome
Link", the connection and entrance building for the two
biomes
The Biome Link responds in plan form to the same
rhythm of interlocking spheres exhibited by the geodesic
structures that it connects Dining and exhibition areas are
bounded by the sweeping perimeter of the front glazed
wall, and separated from back-of-house facilities such as
kitchens, toilets, offices and "plant holding areas" by a
continuously curving double-height earth-rendered wall
Access from the external gardens into the building is via
an elevated walkway, which passes over the external
terrace then penetrates the glazing where it splits, taking
visitors at high level either to the Humid Tropics or the
Warm Temperate biome
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The Biome Link
The perimeter glazed wall achieves solar control by the use
of external cedar louvre screens These allow views directly
in and out of the building, whilst shielding the internal public areas from strong direct sunlight They also lend a layering
to the facade that helps to break down the boundary between internal and external spaces.The Biome Link has a turf roof that curves to align with the adjacent geodesic structures It slopes down at each comer of the building where the surrounding ground slopes up to meet it, so that the overall effect is of a "saddle" of ground covering the Link The roof structure is an array of steel bowstring trusses These vary in shape to accommodate the profile of the curved roof as it transforms from the Humid Tropics arch geometry to the Warm Temperate arch geometry
This self effacing approach hopefully puts the aspirations of the Eden project before any preconceived architectural metaphors We hope that in the same way as the technology
of wrought iron brought about a revolution in the design of the glass house at the start of the nineteenth century, the technologies adopted at Eden will be part of a major step in the development of greenhouse architecture at the beginning
of the twenty-first century
Model of the Humid Tropics Biome
We have been inspired by the elegance and economy of design of airships, more than any other type of constructed form they have to explore maximum efficiencies Perhaps this can be best summarised by the weight of the biomes The humid tropics biome weighs approximately 450,000kg; this is actually less than the weight of the air that the envelope encloses Fortunately
it is firmly bolted down to the ground!
Luftschiffbau Zeppelin airship 129 Hindenburg,